<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <script>
        var a = 0
        var b = async () => {
            a = a + await 10
            console.log('2', a) // -> '2' 10
            a = (await 10) + a
            console.log('3', a) // -> '3' 20
        }
        b()
        a++
        console.log('1', a) // -> '1' 1
        /**
            1 1
            2 10
            3 20
        */
    </script>
</body>

</html>